Spring integration: GatewayHeader: Add headers at Gateway

You can add headers to a message using gateway.

 

How to add headers using @MessagingGateway annotation

‘defaultHeaders’ attribute is used to custom message headers. These default headers are created for all methods on the service-interface.

 

Example

@MessagingGateway(defaultHeaders = {@GatewayHeader(name = "root-header", value = "root123")})
public interface CustomGateway {

}

How to add headers using @Gateway annotation?

'headers' attribute is used specify additional headers that will be added to the request message.

@Gateway(requestChannel = "printChannel", headers = {
		@GatewayHeader(name = "secret", value = "my-secret123"),
		@GatewayHeader(name = "service-name", value = "my-service") })
public String sendToPrintChannel(String message);

 

Find the below working application.

 

Step 1: Create new maven project ‘gateway-headers-demo’.

 

Step 2: Update pom.xml with maven dependencies.

 

pom.xml

 

<project xmlns="http://maven.apache.org/POM/4.0.0"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.sample.app</groupId>
	<artifactId>gateway-headers-demo</artifactId>
	<version>1</version>

	<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-parent -->
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.4.0</version>
	</parent>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-integration</artifactId>
		</dependency>

	</dependencies>

</project>

Step 3: Define gateway.

 

CustomGateway.java

package com.sample.app.gateway;

import org.springframework.integration.annotation.Gateway;
import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.integration.annotation.*;

@MessagingGateway(defaultHeaders = {@GatewayHeader(name = "root-header", value = "root123")})
public interface CustomGateway {

	@Gateway(requestChannel = "printChannel", headers = {
			@GatewayHeader(name = "secret", value = "my-secret123"),
			@GatewayHeader(name = "service-name", value = "my-service") })
	public String sendToPrintChannel(String message);

}

Step 4: Define service activator.

 

PrintService.java

package com.sample.app.service;

import java.util.Map;
import java.util.Set;

import org.springframework.integration.annotation.ServiceActivator;
import org.springframework.messaging.Message;
import org.springframework.stereotype.Component;

@Component
public class PrintService {

	@ServiceActivator(inputChannel = "printChannel")
	public String consumeStringMessage(Message<String> message) {
		System.out.println("Received message from printChannel : " + message.getPayload());
		
		Set<Map.Entry<String, Object>> messageHeaders = message.getHeaders().entrySet();
		
		System.out.println("Headers are.....");
		for(Map.Entry<String, Object> entry: messageHeaders) {
			System.out.println(entry.getKey() + " -> " + entry.getValue());
		}
		
		return "Success";
	}
	

}

Step 5: Define main application class.

 

App.java

package com.sample.app;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.sample.app.gateway.CustomGateway;

@SpringBootApplication
@Configuration
public class App {

	@Autowired
	private CustomGateway customGateway;

	public static void main(String[] args) {
		SpringApplication.run(App.class, args);
	}

	@Bean
	public CommandLineRunner demo() {
		return (args) -> {

			String reply = customGateway.sendToPrintChannel("Hello World");
			
			System.out.println("reply : " + reply);
		};

	};

}

Total project structure looks like below.

Run App.java, you will see below messages in console.

Received message from printChannel : Hello World
Headers are.....
service-name -> my-service
replyChannel -> org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@64712be
errorChannel -> org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel@64712be
root-header -> root123
secret -> my-secret123
id -> f3f45661-6f2e-b0c4-5503-04c302aeb937
timestamp -> 1617701164345
reply : Success

You can download complete working application from below link.

https://github.com/harikrishna553/springboot/tree/master/spring-integration/gateway-headers-demo

 

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